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loss in insoluble sodium compounds left behind in the black 
ash and waste, Wright states that it forms the largest item 
of the several individual losses, making up the total 2024 
per cent loss out of 100 parts Na 2 0 as salt cake occurring 
in the practical conversion of salt cake to soda ash, Wright 
tabulates this as follows : 
Previous to lixiviation of the black ash. 
XJndecomposed sodium sulphate 3*49 
Insoluble sodium compounds 5*44 
Vaporisation, &c., of sodium compounds 1*14 
During and after lixiviation. 
Soluble alkali left in vat waste 3*61 
Leakage and losses in soda ash process ... 6 ‘5 6 
Total loss per cent 20-24 
In experiments tried with samples of black ash Wright 
showed that on prolonged boiling (6 hours) with water, 
the insoluble sodium compound in the black ash residue 
was decomposed, and yielded a sodium salt in solution 
capable of neutralising acid. On taking soda waste 
and submitting this to prolonged boiling with water, only 
3 -81 out of 5 ‘08 per cent of the insoluble soda, calculated as 
NaaCOg, were extractible, and he considers that this differ- 
ence from his experience with the black ash, is due to the 
influence of the other sodium salts present on the insoluble 
compound in the case of the black ash. Wright also cites 
the well known fact, that on causticising sodium carbonate 
solutions with quicklime, the calcium carbonate formed 
retains a considerable portion of sodium in an insoluble 
form, and adds, that most probably in the case of the black 
ash a double sodium calcium carbonate is formed, either in 
the furnace or on addition of water to the crude soda. In 
further proof of this view he mentions the case of some ex- 
perimental charges for black ash, in which an unusual excess 
